Three-dimensional article and method of making the same

ABSTRACT

Three-dimensional polymeric article ( 100 ) having first ( 101 ) and second ( 102 ) opposed major surfaces, a base body ( 103 ) having a first dimension, a second dimension perpendicular to the first dimension, and a thickness, wherein the thickness is orthogonal to the first and second dimensions, wherein the base body ( 103 ) comprises a plurality of alternating, adjacent first ( 107 ) and second ( 108 ) polymeric regions along the first dimension, wherein the second dimensions of the first ( 107 ) and second ( 108 ) regions extend at least partially across the second dimensions, wherein the first regions ( 107 ) have a first crosslink density, wherein the second regions ( 108 ) have a second crosslink density, wherein the second crosslink density of the second regions ( 108 ) are less than the first crosslink density of the first regions ( 107 ), wherein the first and second regions extend perpendicularly in two directions from a central plane ( 115 ) in the base body ( 103 ) parallel to the first and second dimensions of the polymeric article ( 100 ), and wherein the second regions ( 108 ) extend in each of said two directions further than does the first regions ( 107 ). Embodiments of the three-dimensional polymeric article described herein are useful for providing a dual sided, textured wrapping film such that greater grip is realized both on an item wrapped by the film and the wrapped item itself.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2016/067710, filed Dec. 20, 2016, which claims the benefit of U.S.Provisional Application No. 62/271707, filed Dec. 28, 2015, thedisclosure of which is incorporated by reference in its/their entiretyherein.

BACKGROUND

Microstructured films, with features on the micrometer scale, have beenused in a variety of technologies including overhead projector films,reflective signage, and abrasive films. Common microstructure formingprocesses include extrusion, embossing, and lithography (e.g.,photolithography). Lithographic processes often require complex optics,relatively low throughput, and multiple processing steps, includingsolution based processing which may generate significant amounts ofliquid waste. Microreplication processes such as extrusion and hotembossing typically require expensive master pattern rolls for any givenpattern, and any changes to the pattern would require the added expenseof a new master to be fabricated. In addition, the patterns are limitedin both feature depth and type of pattern (e.g., based on diamondturning methods). In addition, the microreplication processes generallyproduce materials having a base plane (sometimes referred to as the“land” area) with patterns protruding either all above or all below thebase plane. Precise registration of microstructured patterns on opposingsides of a film may allow for simultaneous features both above and belowthe base plane, however, these processes are significantly more complexand often have additional limitations on precision of feature placementabove and below the base plane. New microstructured films, and methodsof making them, are desirable.

SUMMARY

In one aspect, the present disclosure describes a three-dimensionalpolymeric article having first and second opposed major surfaces, a basebody having a first dimension, a second dimension perpendicular to thefirst dimension, and a thickness, wherein the thickness is orthogonal tothe first and second dimensions, wherein the base body comprises aplurality of alternating, adjacent first and second polymeric regionsalong the first dimension, wherein the first and second regions extendat least partially across the second dimensions, wherein the firstregions have a first crosslink density, wherein the second regions havea second crosslink density, wherein the second crosslink density of thesecond regions are less (in some embodiments, at least 1% less, 2% less,3% less, 4% less, 5% less, 10% less, 15% less, 20% less, 25% less, 30%less, 35% less, 40% less, 45% less, 50% less, 55% less, 60% less, 65%less, 70% less, 75% less, 80% less, 85% less, 90% less, 95% less, oreven 100% less) than the first crosslink density of the first regions,wherein the first and second regions extend perpendicularly in twodirections from a central plane in the base body parallel to the firstand second dimensions of the polymeric article, and wherein the secondregions extend in each of said two directions further than does thefirst regions.

In another aspect, the present disclosure describes a method comprising:

providing an oriented, crosslinkable film having first and secondopposed major surfaces;

irradiating (e.g., with e-beam, ultraviolet (UV), x-ray, and/or gammaradiation) through at least a portion of the first major surface of theoriented, crosslinkable film to cause at least some portions under thefirst major surface to be irradiated and at least partially crosslink toprovide first irradiated portions, wherein there remain after saidirradiating at least second portions that are less irradiated than(which include zero irradiation) the first irradiated portions, andwherein the first irradiated portions have a lower shrink ratio than thesecond irradiated portions; and

dimensionally relaxing (e.g., via heating and/or via removing tension)the irradiated film. It is understood that when irradiating through amajor surface of the film the surface too is irradiated. In someembodiments, the method results in the three-dimensional polymericarticle described herein. In some embodiments of the method, the firstmajor surface is masked to at least reduce exposure of the radiation.

“Crosslink density” as used herein refers to the quotient of the polymerfilm density divided by the average molecular mass between crosslinks,M_(c), as calculated using the Flory-Rehner equation (Equation 1).

$\begin{matrix}{\frac{1}{M_{c}} = {\frac{2}{M_{n}} - {\frac{\frac{v_{s}}{V_{1}}\left( {{\ln\left( {1 - v_{2}} \right)} + v_{2} + {\chi_{1}v_{2}^{2}}} \right)}{v_{2}^{1/3} - \frac{v_{2}}{2}}.}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$wherein,M_(c)=average molecular mass between crosslinks,M_(n)=number-average molecular mass of the un-crosslinked polymer,V₁=molar volume of the solvent,ν₂=polymer volume fraction in the equilibrium swollen gel,ν_(s)=specific volume of the polymer, andχ₁=polymer-solvent interaction parameter.

“Shrink ratio” as used herein refers to the length or width of a pieceof film before dimensionally relaxing divided by the respective lengthor width of the same piece of film after dimensionally relaxing, whereinthe film is dimensionally relaxable in the length or width dimension.

“Dimensionally relaxable” as used herein refers to the property whereinat least one dimension of a material undergoes a reduction in sizeduring the dimensional relaxation process. Dimensional relaxationprocesses include heating of a heat shrinkable film or releasing tensionon a stretched film. The shrink ratio of a film in the length dimensionmay or may not be equivalent to the shrink ratio of a film in the widthdimension. One way to change the shrink ratio of a film is to change thedegree of crosslinking or crosslink density of the film. Irradiatingoriented, crosslinkable films with suitable radiation can increase thecrosslink density of a film, and subsequently decrease the shrink ratioof the irradiated portions of the film. Suitable radiation includeselectron beam, UV, x-ray, and/or gamma radiation.

Embodiments of the three-dimensional polymeric article described hereinare useful, for example, in providing a dual-sided, textured wrappingfilm such that greater grip is realized both on an item wrapped by thefilm and the wrapped item itself.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side-view schematic of an exemplary three-dimensionalpolymeric article described herein.

FIG. 2 is a side-view schematic of another exemplary three-dimensionalpolymeric article.

FIG. 3A is a perspective view scanning electron digital micrograph ofExample 1.

FIG. 3B is an optical image of the top view of Example 1.

FIG. 4A is a cross-sectional view scanning electron digital micrographof Example 1.

FIG. 4B is an optical image of the cross-sectional view of Example 1.

FIG. 5A is a perspective view scanning electron digital micrograph ofExample 2.

FIG. 5B is an optical image of the top view of Example 2.

FIG. 6A is a cross-sectional view scanning electron digital micrographof Example 2.

FIG. 6B is an optical image of the cross-sectional view of Example 2.

FIG. 7A is a top view scanning electron digital micrograph ofIllustrative Example A.

FIG. 7B is an optical image of the top view of Illustrative Example A.

FIG. 8A is a cross-sectional view scanning electron digital micrographof Illustrative Example A.

FIG. 8B is an optical image of the cross-sectional view of IllustrativeExample A.

FIG. 9A is a perspective view scanning electron digital micrograph ofIllustrative Example B.

FIG. 9B is an optical image of the top view of Illustrative Example B.

FIG. 10A is a cross-sectional view scanning electron digital micrographof Illustrative Example B.

FIG. 10B is an optical image of the cross-sectional view of IllustrativeExample B.

DETAILED DESCRIPTION

Referring to FIG. 1, exemplary three-dimensional polymeric article 100has first and second opposed major surfaces 101, 102, a length, a width,and base body 103 comprising plurality of alternating, adjacent firstand second polymeric regions 107, 108 along the length (and/or width;shown as length). Widths of first and second regions 107, 108 extend atleast partially across width. First regions 107 have a first crosslinkdensity. Second regions 108 have a second crosslink density. The firstcrosslink density of the first regions are greater than the secondcrosslink density of the second regions. The first and second regionsextend perpendicularly in two directions from central plane 115 in basebody 103 parallel to the length of polymeric article 100. Second regions108 extend in both of the two directions further than does first regions107.

Three-dimensional polymeric articles described herein can be made, forexample, by:

providing an oriented, crosslinkable film having first and secondopposed major surfaces,

irradiating (e.g., with e-beam, UV, x-ray, and/or gamma radiation)through at least a portion of the first major surface of the oriented,crosslinkable film to cause at least some portions under the first majorsurface to be irradiated and at least partially crosslink to providefirst irradiated portions, wherein there remain after said irradiatingat least second portions that are less irradiated than (which includezero irradiation) the first irradiated portions, and wherein the firstirradiated portions have a lower shrink ratio than the second irradiatedportions; and

dimensionally relaxing (e.g., via heating, via removing tension, etc.)the irradiated film. In some embodiments, the method results in thethree-dimensional polymeric article described herein. In someembodiments of the method, the first major surface is masked to at leastreduce exposure of the radiation to at least portions of the first majorsurface.

Techniques for masking are known in the art and include the use ofaperture masks as well as photomasking as used in lithographicprocesses. In some embodiments, maskless radiation techniques includingelectron beam lithography, x-ray lithography, interference lithography,direct-write digital imaging lithography, and multiphoton lithographycan be used to selectively irradiate through the first major surface.

In some embodiments, the method provides the exemplary article shown inFIG. 2, exemplary three-dimensional polymeric article 200 has first andsecond opposed major surfaces 201, 202, a length, a width, and aplurality of alternating first and second polymeric regions 207, 208along the length (and/or width; length as shown). The widths of thefirst and second regions 207, 208 extend at least partially across thewidth. First regions 207 are in common plane 215. Second regions 208project outwardly from plane 215. As shown, some second regions 208project outwardly from plane 215 in a first direction, and some secondregions 208 project outwardly from plane 215 in a second direction thatis generally 180 degrees from the first direction. First regions 207have a first crosslink density. Second regions 208 have a secondcrosslink density. First crosslink density of the first regions 207 isless than the second crosslink density of the second regions 208. Forfurther details on this exemplary embodiment, see co-pending applicationhaving U.S. Ser. No. 62/271,712 , filed Dec. 28, 2015, the disclosure ofwhich is incorporated herein by reference.

In general, suitable oriented, crosslinkable films possess the abilityto crosslink polymer chains in the film upon irradiation (e.g., byelectron beam, x-ray, UV, and/or gamma radiation) and the property ofbeing dimensionally relaxable, where dimensionally relaxable refers tothe property wherein at least one dimension of a material undergoes areduction in size during the relaxation process. For example,elastomeric materials in a stretched state are dimensionally relaxable,wherein the relaxation process is the release of stretch or strain inthe elastic material. In the case of heat shrink materials, thermalenergy is supplied to the material to allow release of theorientation-induced strain in the heat shrink material. Examples of heatshrinkable materials include polyolefins, polyurethanes, polystyrenes,polyvinylchloride, poly(ethylene-vinyl acetate), fluoropolymers (e.g.,polytetrafluoroethylene (PTFE), synthetic fluoroelastomer (available,for example, under the trade designation “VITON” from DuPont,Wilmington, Del.), polyvinylidenefluoride (PVDF), fluorinated ethylenepropylene (FEP)), silicone rubbers, and polyacrylates. Examples of otheruseful polymeric substrate materials are shape memory polymers such aspolyethylene terephthalate (PET), polyethyleneoxide (PEO),poly(1,4-butadien), polytetrahydrofuran, poly(2-methly-2-oxazoline),polynorbornene, block-co-polymers, and combinations thereof). Examplesof elastomeric materials include natural and synthetic rubbers,fluoroelastomers, silicone elastomers, polyurethanes, and polyacrylates.Suitable oriented, crosslinkable films may be obtained from heat shrinkfilm suppliers, including Sealed Air, Elwood Park, N J, and Clysar,Clinton, Iowa.

Ultraviolet, or “UV,” activated cross-linkers can also be used tocrosslink the film to modulate dimensional relaxation. Such UVcross-linkers may include non-copolymerizable photocrosslinkers, such asbenzophenones and copolymerizable photocrosslinkers such as acrylated ormethacrylated benzophenones like 4-acryloxybenzophenones. Additionally,the use of multifunctional, free radical polymerizable molecules incombination with a photo-induced free radical generator (photoinitiator)may be used to form crosslinked networks under UV irradiation. Examplesof multifunctional, free radical polymerizable molecules would bemultifunctional acrylates such as hexanediol diacrylate ortrimethylolpropane triacrylate, both available from Sartomer, Exton, Pa.Exemplary photoinitiators are available under the trade designations“IRGACURE 651” and “DAROCUR 1173,” available from BASF, Tarrytown, N.Y.

In some embodiments, the oriented, crosslinkable films have a thicknessprior to dimensional relaxation in a range from 1 micrometer to 1000micrometers (in some embodiments, in a range from 5 micrometers to 500micrometers, 10 micrometers to 250 micrometers, or even 10 micrometersto 100 micrometers).

In some embodiments, the oriented, crosslinkable films comprise a fillermaterial (e.g., an inorganic material). Exemplary fillers include beads,bubbles, rods, fibers or particles comprising glass (e.g., soda lime,borosilicate, etc.), ceramic (e.g., oxides of silicon, aluminum,titanium, zirconium, or combinations thereof), metal (e.g., silver,gold, copper, aluminum, zinc) or combination thereof, and/orglass-ceramics.

The polymeric substrate having the irradiated portions thereon can bedimensionally relaxed, for example, via heating and/or removing tension.For example, pre-stretched elastomeric substrates can be relaxed byreleasing the tension holding the substrate in the stretched state. Inthe case of heat shrinkable substrates, the substrates may be placed,for example, in a heated oven or heated fluid until the desiredreduction in dimension is achieved.

In some embodiments, the irradiated substrate has an original length (orwidth) and is dimensionally relaxed in length (or width) by at least 20(in some embodiments, at least 25, 30, 40, 50, 60, 70, or even at least80) percent of the original length (or width). Higher percent changes oforiginal length (or width) upon dimensional relaxation typically producegreater extensions in the substrate after relaxation.

In some embodiments, in the range from 0.5% to 99.5% of the first majorsurface of the three-dimensional polymeric article comprises the firstregions.

In some embodiments, the first and second regions each have an averagethickness, and wherein the average thickness of the second regions is atleast 1 micrometer (in some embodiments, at least 5, 10, 15, 20, 25, 30,35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or even at least 100micrometers) greater than the average thickness of the first regions.The thickness in a given (first or second) region of thethree-dimensional polymeric article is the shortest distance between apoint on the first major surface to the second major surface of thethree-dimensional polymeric article within the given region.

Embodiments of the three-dimensional polymeric article described hereinare useful for providing a dual-sided, textured wrapping film such thatgreater grip is realized both on an item wrapped by the film and thewrapped item itself. ps Exemplary Embodiments

-   1A. A three-dimensional polymeric article having first and second    opposed major surfaces, a base body having a first dimension, a    second dimension perpendicular to the first dimension, and a    thickness, wherein the thickness is orthogonal to the first and    second dimensions, wherein the base body comprises a plurality of    alternating, adjacent first and second polymeric regions along the    first dimension, wherein the second dimensions of the first and    second regions extend at least partially across the second    dimensions, wherein the first regions have a first crosslink    density, wherein the second regions have a second crosslink density,    wherein the second crosslink density of the second regions are less    (in some embodiments, at least 1% less, 2% less, 3% less, 4% less,    5% less, 10% less, 15% less, 20% less, 25% less, 30% less, 35% less,    40% less, 45% less, 50% less, 55% less, 60% less, 65% less, 70%    less, 75% less, 80% less, 85% less, 90% less, 95% less, or even 100%    less) than the first crosslink density of the first regions, wherein    the first and second regions extend perpendicularly in two    directions from a central plane in the base body parallel to the    first and second dimensions of the polymeric article, and wherein    the second regions extend in each of said two directions further    than does the first regions.-   2A. The three-dimensional polymeric article of Exemplary Embodiment    1A having in the range from 0.5% to 99.5% of the first major surface    comprising the first regions.-   3A. The three-dimensional polymeric article of any preceding A    Exemplary Embodiment, wherein the first and second regions comprise    a filler material (e.g., inorganic material).-   4A. The three-dimensional polymeric article of any preceding A    Exemplary Embodiment, wherein the first and second regions each have    an average thickness, and wherein the average thickness of the    second regions is at least 1 micrometer (in some embodiments, at    least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,    85, 90, 95, or even at least 100 micrometers) greater than the    average thickness of the first regions (wherein the thickness in a    given (first or second) region of the three-dimensional polymeric    article is the shortest distance between a point on the first major    surface to the second major surface of the three-dimensional    polymeric article within the given region).-   1B. A method of making the three-dimensional polymeric article, the    method comprising:

providing an oriented, crosslinkable film having first and secondopposed major surfaces,

irradiating (e.g., with e-beam, UV, x-ray, and/or gamma radiation)through at least a portion of the first major surface of the oriented,crosslinkable film to cause at least some portions under the first majorsurface to be irradiated and at least partially crosslink to providefirst irradiated portions, wherein there remain after said irradiatingat least second portions that are less irradiated than (which includezero irradiation) the first irradiated portions and, wherein the firstirradiated portions have a lower shrink ratio than the second irradiatedportions; and

dimensionally relaxing (e.g., via heating and/or via removing tension)the irradiated film.

-   2B. The method of Exemplary Embodiment 1B, wherein portions of the    first major surface are masked to at least reduce exposure of the    radiation through at least portions of the first major surface.-   3B. The method of Exemplary Embodiment 1B or 2B that provides a    three-dimensional polymeric article of any preceding A Exemplary    Embodiment.

Advantages and embodiments of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. All parts andpercentages are by weight unless otherwise indicated.

EXAMPLES

Materials

Designation Description PO Heat Shrink Film Polyolefin (PO) heat shrinkfilm, 25 micrometers, shrink ratio ~4.4:1, (25 micrometers) (obtainedfrom Sealed Air, Elmwood Park, NJ, under trade designation “CRYOVACD-955”) was laminated to a 3 mil (75 micrometer) polyethyleneterephthalate (PET) film with a thin film of latex emulsion pressuresensitive adhesive (PSA) to form a multilayer film that is easier tohandle. The PO heat shrink film layer was peeled away from the PSA/PETfilm prior to heating. PO Heat Shrink Film Polyolefin (PO) heat shrinkfilm, 19 micrometers, shrink ratio ~4.4:1, (19 micrometer)s (obtainedfrom Sealed Air, Elmwood Park, NJ, under trade designation “CRYOVACD-955”). Circular Hole Array Perforated aluminum plate, 1/16″ (1.59 mm)thick, with hexagonal array Mask-I of circular holes 3/32″ (2.38 mm)diameter holes (obtained from Amazon.com, under trade designation “ASID:B004OR1A7C). Circular Hole Array Perforated aluminum plate, 1/16″ (1.59mm) thick, with hexagonal array Mask-II of circular holes 3/16″ (4.76mm) diameter holes (obtained from Amazon.com under trade designation“ASID: B004OR1A7C”).MethodsMethod for Electron Beam Irradiation of Film Substrates

All electron beam (e-beam) irradiation was performed using an electronbeam source (obtained under trade designation “ELECTROCURTAIN” fromEnergy Sciences, Inc. (ESI), Wilmington, Del.) running at 300 kV. The POheat shrink film samples were taped with a polyester tape (obtained from3M Company under trade designation “3M POLYESTER TAPE 8403”) onto acarrier web of PET film running at 18.9 ft./min. (5.76 m/min.) into thee-beam chamber. E-beam dose was controlled to deliver 2.5-40 Mrad in asingle pass through the e-beam or cumulatively in multiple passes.

Method for Dimensionally Relaxing Substrates

Small pieces about 5 cm×5 cm (˜2 inches×˜2 inches) in size of theirradiated PO heat shrink film were cut with a pair of scissors andheated to convert to their “relaxed states.” More specifically, the heatshrink films were placed between two polytetrafluoroethylene (PTFE) meshscreens and placed in a preheated oven at 145° C. (air temperature) forabout 45 to 120 seconds before rapidly removing and cooling to about 40°C. within 1 minute.

Method for Optical Microscopy

Optical images were obtained using a microscope (obtained under thetrade designation “ZEISS STEMI 2000-C” from Allied High Tech Products,Inc., Rancho Dominguez, Calif.) with a digitizer (obtained under thetrade designation “AXIOCAM ICC3” from Allied High Tech Products, Inc.,Rancho Dominguez, Calif.) for digital image capture via a computer.

Method for Scanning Electron Microscopy

Images were obtained using a Scanning Electron Microscope (SEM)(obtained from JEOL Inc., Tokyo, Japan, under the trade designation“JEOL BENCH TOP SEM”). A 45° angle mount (obtained from Ted Pella, Inc.,Redding, Calif., under trade designation “PELCO SEM CLIP 45/90° MOUNT”(#16357-20)) was used for mounting samples in the SEM. A small piece ofconductive carbon tape (obtained from 3M Company, St. Paul, Minn., tradedesignation “3M TYPE 9712 XYZ AXIS ELECTRICALLY CONDUCTIVE DOUBLE SIDEDTAPE”) was placed at the top of the 45° angle surface of the mount, andsamples were mounted by affixing a small piece of the film/tube onto thecarbon tape. If possible, the sample piece was situated as close to thetop edge of the 45° angle surface as possible. A small amount of silverpaint (obtained from Ted Pella, Inc., Redding, Calif., under tradedesignation “PELCO CONDUCTIVE LIQUID SILVER PAINT” (#16034)) was thenapplied to a small region of each sample piece, and extended to contacteither the carbon tape, aluminum mount surface or both. After brieflyallowing the paint to air dry at room temperature, the mounted sampleassembly was placed into a sputter/etch unit (obtained from DentonVacuum, Inc., Moorestown, N.J., under the trade designation “DENTONVACUUM DESK V”) and the chamber was evacuated to ˜0.04 Torr (5.33 Pa).Argon gas was then introduced into the sputtering chamber until thepressure stabilized at ˜0.06 Torr (8.00 Pa) before initiating the plasmaand sputter coating gold onto the assembly for 90-120 seconds at ˜30 mA.

Cross-sectional images through the thickness of the films were obtainedby orienting the sample 90 degrees relative to the beam. Thicknessmeasurements were obtained from the image using the length measuringfeature in the software (obtained under the trade designation“JCM-5000,” version 1.2.3 from JEOL Inc.). Thickness in a given (firstor second) region of the film was measured as the shortest distancebetween a point on the first major surface to the second major surfaceof the film. For each region thickness, three separate locations withinthe region were measured and averaged.

Method for Measuring Swell Ratio

Swell Ratio was measured using ASTM D2765-01 (2006) (Test Method C), thedisclosure of which is incorporated herein by reference. Samples ofe-beam irradiated PO heat shrink film (19 micrometer) were immersed in110° C. xylenes for 20 hours. Samples were weighed after the immersionperiod while wet and swollen, and again after drying.

Method for Calculating Crosslink Density

Crosslink density was calculated by dividing the density of the polymerfilm by the average molecular mass between crosslinks, M_(c). Theaverage molecular mass between crosslinks, M_(c), was calculated usingthe Flory-Rehner equation (Equation 1).

$\begin{matrix}{\frac{1}{M_{c}} = {\frac{2}{M_{n}} - {\frac{\frac{v_{s}}{V_{1}}\left( {{\ln\left( {1 - v_{2}} \right)} + v_{2} + {\chi_{1}v_{2}^{2}}} \right)}{v_{2}^{1/3} - \frac{v_{2}}{2}}.}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$wherein,M_(c)=average molecular mass between crosslinks,M_(n)=number-average molecular mass of the un-crosslinked polymer,V₁=molar volume of the solvent,ν₂=polymer volume fraction in the equilibrium swollen gel,ν_(s)=specific volume of the polymer, andχ₁=polymer-solvent interaction parameter.

The polymer volume fraction in the equilibrium swollen gel, is thereciprocal of the swell ratio, Q. Under the conditions described in thesection “Method for Measuring Swell Ratio”, Q, the molar volume of thesolvent (xylenes), V₁, is 135.89 cm³/mole at 110° C., as calculated fromthe reciprocal of the density of xylenes at 110° C. The specific volumeof the polymer, ν_(s), is the reciprocal of the density of the polymer.The density of PO heat shrink film is 0.7 g/cm³ (as reported in U.S.Pat. No. 6,340,532 B1 (Bormann et al.), Comparative Example 3, Table 4),and therefore ν_(s) is 1.084 cm³/g. The polymer-solvent interactionparameter, χ₁, used for low density polyethylene and xylenes at 120-140°C. is 0.28 and was obtained from Physical Properties of PolymersHandbook, AIP Press, New York, 1996, Chapter 14, Table 14.1. For thecalculations herein, an estimated M_(n) value of 27,300 g/mol was used.

Method for Calculation of Critical Unit Compressive Stress

Upon dimensional relaxation, the masked (less irradiated) regions of thepolymeric article have a higher shrink ratio and compress the unmasked(more irradiated) regions having a lower shrink ratio. The critical unitcompressive stress, σ′ (i.e., buckling instability limit), is the stresslimit above which an object will buckle and/or distort. The unmasked(exposed to e-beam radiation) regions in the Examples and IllustrativeExamples are circular in form with a thickness (i.e., a circular plate).Equation 2 (below) was used to estimate the critical unit compressivestress, σ′ (i.e., buckling instability limit) of a circular plate beingacted upon by a uniform radial edge compression as described in Young,W. C., Budynas, R. G., 2001, Roark's Formulas for Stress and Strain, 7thEd., New York, McGraw-Hill Professional, p. 734, Table 15.2.

$\begin{matrix}{{\sigma^{\prime} = {K \cdot \frac{E}{1 - v^{2}} \cdot \left( \frac{t}{a} \right)^{2}}}{\begin{matrix}v & 0 & 0.1 & 0.2 & 0.3 & 0.4 \\K & 0.282 & 0.306 & 0.328 & 0.350 & 0.370\end{matrix}.}} & {{Equation}\mspace{14mu} 2}\end{matrix}$wherein,K=Column effective length factor,E=Modulus of elasticity,ν=Poisson's ratio,a=Radius of circular plate, andt=Thickness of circular plate.

A Poisson's ratio (ν) of 0.46 (and therefore, K ˜0.370) was used (basedon data for polyethylene as reported in[http://www.goodfellow.com/E/Polyethylene-High-density.html]) for POheat shrink film (obtained under the trade designation “CRYOVAC D-955”from Sealed Air, Elmwood Park, N.J.).

The elastic modulus (E), for the heat shrink film (“CRYOVAC D-955”) wasbetween 60,000 psi and 65,000 psi (413 MPa and 448 MPa, respectfully)for the longitudinal and transverse film directions, respectively, asreported in Technical Data Sheet for the “CRYOVAC D-955” PO heat shrinkfilm.

The radius (a) and thickness (t) of the resulting exposed circular holeregion was calculated assuming that no buckling in the hole (unmasked)region occurred after shrinking of the masked, irradiated PO heat shrinkfilm by using the shrink ratio of the film in the hole (unmasked)regions. The shrink ratio of the hole (unmasked) regions was determinedby measuring the length and width of an unmasked, irradiated film beforeand after irradiation and dimensional relaxation using a digital caliper(obtained under the trade designation “MODEL TRESNA EC16 SERIES,111-101B,” 0.01 mm resolution, ±0.03 accuracy, from Guilin GuangluMeasuring Instruments Co., Ltd., Guilin, China). Thickness measurementswere taken as the distance between the highest and lowest points in theoverall film. Since, electron beam radiation can reduce the shrink ratioof PO heat shrink film depending on the dose as a result of the extentof crosslinking, shrink ratios of the PO heat shrink film weredetermined after exposing (as described above under “Method for ElectronBeam Irradiation of Film Substrates”) the film to various doses ofelectron beam radiation as reported in Table 1A, below. Samples in Table1A were 25-micrometer thick Polyolefin (PO) heat shrink films beforeshrinking and were placed in a preheated oven at 145° C. for 45 seconds.Calculated crosslink density values for PO heat shrink film irradiatedat 0, 2.5, 5, 10, and 20 Mrad are summarized in Table 1B, below. Samplesin Table 1B were 19-micrometer thick polyolefin (PO) heat shrink filmsbefore shrinking and were placed in a preheated oven at 145° C. for 120seconds.

TABLE 1A Thickness Shrink after Dose/pass, # of Total Dose, Shrink RatioRatio shrinking, Mrads passes Mrads (width) (length) mm 0 0 0 5.07 4.550.57 5 1 5 3.47 3.30 0.30 10 1 10 2.78 2.87 0.18 20 1 20 2.13 2.03 0.1020 2 40 1.66 1.71 0.06

TABLE 1B Crosslink Total Shrink Shrink density, Dose, Ratio RatioThickness after (×10⁻⁵) Mrads (width) (length) shrinking, mm Swell Ratiomol/cm³ 0 4.77 5.17 0.45 Undefined* 0*   2.5 3.58 4.21 0.30 422 6.76 53.29 3.40 0.21 75.1 6.88 10 2.53 2.72 0.14 21.3 7.89 20 2.24 2.39 0.1112.5 9.76 *No gel remained after the immersion in hot xylenes, implyinglittle to no (stable) crosslinking of the polymer is present in thissample under the test conditions.

Examples 1 and 2, Illustrative Examples A and B

Example (EX1), Example (EX2), Illustrative Example A (IE-A), andIllustrative Example B (IE-B) samples were prepared as described abovein the “Method for Electron Beam Irradiation of Film Substrates”section. Table 2, below, summarizes the substrates, masks, and totaldose for each sample in EX1, EX2, IE-A, and IE-B. Examples in Table 2were 25-micrometer thick Polyolefin (PO) heat shrink films beforeshrinking and were placed in a preheated oven at 145° C. for 45 seconds.

TABLE 2 Number Total First Region Second Region Dose/Pass, of Dose,Thickness, Thickness, Example Substrate Mask Mrad Passes Mradmicrometers micrometers EX1 PO heat Circular 20 1 20 113 307 shrink Holefilm Array Mask-I EX2 PO heat Circular 10 1 10 250 390 shrink Hole filmArray Mask-II IE-A PO heat Circular 20 2 40 233 320 shrink Hole filmArray Mask-I IE-B PO heat Circular 20 1 20 137 313 shrink Hole filmArray Mask-II

Various optical images of EX1, EX2, IE-A, and IE-B are shown in FIGS.3A-10B.

FIG. 3A is a perspective view scanning electron digital micrograph ofExample 1.

FIG. 3B is an optical image of the top view of Example 1.

FIG. 4A is a cross-sectional view scanning electron digital micrographof Example 1.

FIG. 4B is an optical image of the cross-sectional view of Example 1.

FIG. 5A is a perspective view scanning electron digital micrograph ofExample 2.

FIG. 5B is an optical image of the top view of Example 2.

FIG. 6A is a cross-sectional view scanning electron digital micrographof Example 2.

FIG. 6B is an optical image of the cross-sectional view of Example 2.

FIG. 7A is a top view scanning electron digital micrograph ofIllustrative Example A.

FIG. 7B is an optical image of the top view of Illustrative Example A.

FIG. 8A is a cross-sectional view scanning electron digital micrographof Illustrative Example A.

FIG. 8B is an optical image of the cross-sectional view of IllustrativeExample A.

FIG. 9A is a perspective view scanning electron digital micrograph ofIllustrative Example B.

FIG. 9B is an optical image of the top view of Illustrative Example B.

FIG. 10A is a cross-sectional view scanning electron digital micrographof Illustrative Example B.

FIG. 10B is an optical image of the cross-sectional view of IllustrativeExample B.

Table 3, below, summarizes the calculated expected values of radius (a),thickness (t), and critical unit compressive stress for the exposedcircular hole regions in EX1, EX2, IE-A, and IE-B. The expected radiusvalues (a) in Table 3 (below) were calculated by taking the product ofhole radius and average shrink ratio values of width and length fromTable 1 (above). The expected thickness values (t) in Table 3 (below)were taken from Table 1A, based on the corresponding Total Dose. Themasked (less irradiated) regions were assumed to have a Total Dose near0 Mrad.

TABLE 3 Total Critical Hole Dose, Unit Compressive Example Radius, mmMrad T, mm a, mm Stress, MPa EX 1 1.190 20 0.1 0.56 6.47 EX 2 2.381 100.18 1.12 5.24 IE-A 1.190 40 0.06 0.56 2.33 IE-B 2.381 20 0.1 1.12 1.62

Based on the data from “CRYOVAC D-955” PO heat shrink film TechnicalData Sheet, the shrink tension for the “CRYOVAC D-955” PO heat shrinkfilm was ˜600 psi (4.14 MPa). Although not wanting to be bound bytheory, comparing the calculated critical unit compressive stress and POheat shrink film tension values in Table 3 (above), it appears there isa correlation as to whether exposed hole regions will buckle or remainplanar during and after shrinking of the film. Although not wanting tobe bound by theory, it appears that to obtain the structures of theExamples (e.g., as shown in FIGS. 1, 3A-6B), the critical unitcompressive stress, σ′ (i.e., buckling instability limit), of anyunmasked region should be greater than the compressive stress of thesurrounding shrinking film region.

Foreseeable modifications and alterations of this disclosure will beapparent to those skilled in the art without departing from the scopeand spirit of this invention. This invention should not be restricted tothe embodiments that are set forth in this application for illustrativepurposes.

What is claimed is:
 1. A three-dimensional polymeric article havingfirst and second opposed major surfaces, a base body having a firstdimension, a second dimension perpendicular to the first dimension, anda thickness, wherein the thickness is orthogonal to the first and seconddimensions, wherein the base body comprises a plurality of alternating,adjacent first and second polymeric regions along the first dimension,wherein the second dimensions of the first and second regions extend atleast partially across the second dimensions, wherein the first regionshave a first crosslink density, wherein the second regions have a secondcrosslink density, wherein the second crosslink density of the secondregions are less than the first crosslink density of the first regions,wherein the first and second regions extend perpendicularly in twodirections from a central plane in the base body parallel to the firstand second dimensions of the polymeric article, and wherein the secondregions extend in each of said two directions further than does thefirst regions.
 2. The three-dimensional polymeric article of claim 1,wherein the second crosslink density of the second regions are less than1 percent the first crosslink density of the first regions.
 3. Thethree-dimensional polymeric article of claim 1 having in the range from0.5% to 99.5% of the first major surface comprising the first regions.4. The three-dimensional polymeric article of claim 1, wherein the firstand second regions comprise a filler material.
 5. The three-dimensionalpolymeric article of claim 1, wherein the first and second regions eachhave an average thickness, and wherein the average thickness of thesecond regions is at least 1 micrometer greater than the averagethickness of the first regions.
 6. A method of making thethree-dimensional polymeric article of claim 1, the method comprising:providing an oriented, crosslinkable film having first and secondopposed major surfaces, irradiating through at least a portion of thefirst major surface of the oriented, crosslinkable film to cause atleast some portions under the first major surface to be irradiated andat least partially crosslink to provide first irradiated portions,wherein there remain after said irradiating at least second portionsthat are less irradiated than the first irradiated portions and, whereinthe first irradiated portions have a lower shrink ratio than the secondirradiated portions; and dimensionally relaxing the irradiated film. 7.The method of claim 6, wherein irradiating is conducted via at least oneof e-beam, UV, x-ray, or gamma radiation.
 8. The method of claim 6,wherein portions of the first major surface are masked to at leastreduce exposure of the radiation to the first major surface.